The invention relates to a method and an arrangement for determining a mass value representing the mass of a vehicle.
The mass value represents the mass of a vehicle.
From the state of the art, systems for controlling (open loop and/or closed loop) the driving dynamics in motor vehicles are known. Here, the driving of the brake systems is of primary concern. In such systems, the knowledge of the vehicle mass with the greatest possible accuracy is of great importance.
If the motor vehicle is a commercial vehicle having a tractor vehicle and a trailer/wagon, then an optimal matching of the braking forces in the sense of economy, safety and driving comfort can be obtained when the masses of the tractor vehicle and the trailer/wagon are known with the greatest precision. If the mass of the entire entity is known, then, for a known mass of the tractor vehicle, the mass of the trailer/wagon can be determined. In commercial vehicles, large differences in the loading and therefore in the entire mass of the vehicle can occur. For this reason, the entire mass and the mass distribution between tractor vehicle and trailer/wagon must be always newly determined. Accordingly, the driving stability can be increased by a suitable distribution of the braking torques to the individual wheel brakes.
A determination of the total mass of a vehicle is known from German patent application DE 42 28 413. In this determination, the vehicle longitudinal acceleration and the corresponding drive forces are measured at two different sequential time points (close in time to each other) during an acceleration operation of the vehicle. The vehicle mass can be determined in dependence upon the measured quantities. Here, it is assumed that the traveling resistance during the mass determination does not significantly change, for example, because of a change of the inclination of the roadway.
The object of the present invention is to show a most precise and simple mass determination while considering a roadway.
As already mentioned, the invention relates to the determination of a mass value representing the mass of a vehicle and especially of a commercial vehicle. The vehicle includes a drive unit and a coupling unit. By opening the coupling unit, the force flow between the drive unit and the vehicle wheels can essentially be interrupted. According to the invention, at least a first acceleration value is detected which represents the vehicle acceleration at a first time point. At this first time point, the coupling unit is essentially closed. Furthermore, at least a first drive value is detected which represents the drive force or the drive torque of the drive unit at the first time point. The essence of the invention is that at least a second acceleration value is detected which represents the vehicle acceleration at a second time point at which the coupling unit is essentially open. Then, a comparison of the detected second acceleration value to at least one pregiven threshold value takes place. According to the invention, the determination of the mass value takes place at least in dependence upon the comparison and at least in dependence upon the detected first acceleration value and the detected first drive value.
With the comparison according to the invention, a roadway slope is detected, whereby a defective mass determination, which is caused by the roadway slope, is avoided without a further sensor being necessary for the determination of the mass and/or for the determination of the slope of the roadway. The mass can be determined during a single acceleration operation and the algorithm according to the invention is easily applied. Here, it has been shown that the result of the mass estimation, which is achieved with the invention, is adequately precise in practice.
It is especially advantageous that it is determined with respect to the comparison of the invention whether the detected second acceleration value lies within an interval. The acceleration values within this interval represent a travel on an essentially level roadway.
If in the comparison of the invention, it is determined that the detected second acceleration value lies outside of the interval, then the mass value is advantageously determined in dependence upon the detected second acceleration value especially in the sense of a correction caused by the inclination of the roadway. In this way, one obtains a generally preliminary mass value even for an inclined roadway with this mass value being burdened with an error under some circumstances.
To improve the mass determination, it is advantageous that at least a first and a second roadway resistance value are determined at least in dependence upon two detected first acceleration values and two detected first drive values at time points at which the clutch is engaged. One of the determined running resistance values is then applied to determine the mass value. It is especially provided that the mean value of at least two of the determined running resistance values is determined as mass value.
The specific running resistance values can be lowpass filtered to avoid unwanted signal fluctuations.
If, for the determination of the mass value or for the determination of the running resistance values, a value representing the vehicle speed and/or a value representing the rotational speed of the vehicle wheels is applied, then the influence of the air dynamic drag and/or the inertial torques of the vehicle wheels can be considered in the mass determination.